FR: general improvements on message detective view
As on 1.9, the message detective has got some suggestions for improvements on issues #502 (closed) and #517 (closed), so I decided to compile them plus some more improvements into a very ugly mockup, which I believe expresses the options we could provide:
Additionally we would allow search for the message id, as this is a known value by the users (some mail clients expose it on the UI, but it's possible to get it via the message source code).
I also added a "swap" button, to allow easily to swap the sender and recipient fields, for convenience.
This is the admin view, which offers all possibilities.
The public view would be more limited, always requiring the full address for both sender and receiver.